Color grading apparatus is utilized to detect the color of products, especially food products, for separating those having a color outside selected limits. Such separation might be used to delete spolled or blemished products as well as those overripe or underripe.
In addition, such color grading apparatus can be used to control processes wherein a color change results from the process. In the cooking of potato chips, for instance, the cooking temperature of the chips can be regulated by detecting the color of the chips as they leave the oven. The resulting color-responsive signal can be compared to a reference signal indicating the product color desired to control the process for cooking the product so that the desired color is obtained.
A major problem in such systems results from the tendency of the light-emitting device to vary light wave length emitted with usage, thereby rendering the color indication erroneous. Such change can result from deterioration of the light source which will change the intensity or the wavelength of the light directed onto the product. A more common problem results from the deposit of moisture, cooking oil or other film on the light-emitting head or lens which film tends to filter or reduce the intensity of the light. For instance in the monitoring of a cooking process, the product coming out of the oven is surrounded by heated cooking oil and moisture-laden air. Fumes naturally rise around the color grading apparatus and in a short time can result in the formation of deposits on the light-emitting head. Any such deposits serve to obstruct the passage of light from the head to the product and filter certain light wavelengths to make the subsequent color reading erroneous in indicating the true color of the product.
This invention relates to an improvement in color grading apparatus of the type described in U.S. Pat. No. 4,057,352, Color Grading Apparatus Utilizing Infrared Light Source, R. Babb, issued on Nov. 8, 1977, and U.S. Pat. No. 3,998,555, Color Grading Apparatus, R. Babb, issued on Dec. 21, 1976.
It is the purpose of the subject invention to provide a color grading apparatus which automatically calibrates so the readout signal indicating color is adjusted for differing light conditions.